mastectomy       
noun [ C ] uk/mæsˈtek.tə.mi/ us/mæsˈtek.tə.mi/
 乳房切除术
a medical operation to remove a woman's breast
  a partial mastectomy (= when part of the breast is removed) 部分乳房切除 
 a double mastectomy (= when both breasts are removed) 双乳切除